Caution should be taken in dating early "fabric" on
the evidence of a single item, as recycling of materials is not
a mid-20th century innovation. Carpenters have been reusing materials,
sheathing, and framing members in the interest of economy for
centuries. Therefore, any analysis of the materials found, such
as nails or sawmarks on the wood, requires an accurate knowledge
of the history of local building practices before any final conclusion
can be accurately reached. It is helpful to establish a sequence
of construction history for the roof and roofing materials; any
historic fabric or pertinent evidence in the roof should be photographed,
measured, and recorded for future reference.
During the repair work, useful evidence might unexpectedly appear.
It is essential that records be kept of any type of work on a
historic building, before, during, and after the project. Photographs
are generally the easiest and fastest method, and should include
overall views and details at the gutters, flashing, dormers, chimneys,
valleys, ridges, and eaves. All photographs should be immediately
labeled to insure accurate identification at a later date. Any
patterning or design on the roofing deserves particular attention.
For example, slate roofs are often decorative and have subtle
changes in size, color, and texture, such as a gradually decreasing
coursing length from the eave to the peak. If not carefully noted
before a project begins, there may be problems in replacing the
surface. The standard reference for this phase of the work is
Recording Historic Buildings, compiled by Harley J. McKee for
the Historic American Buildings Survey, National Park Service,
Washington, D.C., 1970.
 Good design and quality materials for the roof surface, fastenings, and flashing minimize failures. Photo: NPS files. |
Professional advice will be needed to assess the various aspects
of replacing a historic roof. With some exceptions, most historic
roofing materials are available today. If not, an architect or
preservation group who has previously worked with the same type
material may be able to recommend suppliers. Special roofing materials,
such as tile or embossed metal shingles, can be produced by manufacturers
of related products that are commonly used elsewhere, either on
the exterior or interior of a structure. With some creative thinking
and research, the historic materials usually can be found.
Craft Practices: Determining the craft practices used in the installation
of a historic roof is another major concern in roof restoration.
Early builders took great pride in their work, and experience
has shown that the " rustic" or irregular designs commercially
labeled "Early American" are a 20th-century invention.
For example, historically, wood shingles underwent several distinct
operations in their manufacture including splitting by hand, and
smoothing the surface with a draw knife. In modern nomenclature,
the same item would be a "tapersplit" shingle which
has been dressed. Unfortunately, the rustic appearance of today's
commercially available "handsplit" and re-sawn shingle
bears no resemblance to the handmade roofing materials used on
early American buildings.
Early craftsmen worked with a great deal of common sense; they
understood their materials. For example they knew that wood shingles
should be relatively narrow; shingles much wider than about 6"
would split when walked on, or they may curl or crack from varying
temperature and moisture. It is important to understand these
aspects of craftsmanship, remembering that people wanted their
roofs to be weather-tight and to last a long time. The recent use
of "mother goose" shingles on historic structures is
a gross underestimation of the early craftsman's skills.
"Roofing" an Historic Preservation Brief
